T19P E2 auto provision firmware.

[NI]

Hello, I have some phones T19P E2. With default firmware 53.80.14.2.
I want to update my phones with original firmware from yealink.com
I download firmware version: 19P_E2-53.81.0.110 and manually update my phones to this version. After I update with auto provision to version T19P_E2-53.83.0.35 with no problem. But after I try to update to firmware version T19P_E2-53.83.0.50 and get error. I want it's temporarily problem and after release T19P_E2-53.84.0.10 I try to update again and fail too. But if i try to update from 53.81.0.110 to 53.84.0.10 i don't have error. If I update manually from web interface - it's not error.
I try to understand problem and start syslog for update from 53.83.035 to 53.84.0.10.

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Add syslog with manually update from 53.83.0.35 to 53.81.0.110 and automatically update with help autoprovision from 53.81.0.110 to 53.84.0.10. May be it's help to solve problem.

[NI]

I found solution my problem.

Default value for parameter static.auto_provision.attempt_expired_time is 5 seconds. But on 100 Mbps ethernet phone can download 7565456 bytes, but size of new rom is 7565584 bytes and phone can't correct download new rom file for normal update. If increase static.auto_provision.attempt_expired_time to 6 or more seconds you can updating done.